1. Field of the Invention
The present invention relates generally to a fuel injection valve for an automotive vehicle and more specifically to a saw-toothed solenoid type fuel injection valve by which fuel injection timing and period can be controlled electromagnetically at a high speed under a high fuel injection pressure.
2. Description of the Prior Art
An electromagnetic fuel injection valve for controlling fuel injection rate for an automotive engine has been used with an electrically controlled fuel injection unit for supplying fuel into the intake channel of an engine. However, since the injection valve can be used only under a low fuel injection pressure such as several kg/cm.sup.2, it is impossible to use this valve in order to directly inject fuel into a high-pressure combustion chamber such as those used with diesel engines.
On the other hand, in the case of a diesel engine or an injection-in-cylinder type engine with ignition plugs, it is important to accurately control the fuel injection timing and fuel injection period from the standpoints of improving the fuel consumption rate and exhaust gas quality (against excess unburned hydrocarbon content). However, it has heretofore been impossible to sufficiently and accurately control the injection timing and the period by the use of conventional mechanical fuel injection valves which are opened or closed only by fuel pressure.
Therefore, there has been a strong need for an electromagnetic fuel injection valve whose open/close timing can be easily and freely controlled. However, fuel injection pressure may be as high as approximately 100 kg/cm.sup.2 and therefore it is necessary to press the valve against the valve seat by a high tension spring; accordingly, a solenoid having a great actuating power is needed in order to open or close the valve element freely. Consequently, the solenoids used are large in shape and heavy in weight, thus resulting in slower responsiveness when used with a high speed engine such as an injection-in-cylinder type engine with ignition plugs.